In arid areas of the world water is becoming one of the most precious natural resources. Meeting future water needs in these arid areas may require aggressive conservation measures. This requires irrigation systems that apply water to the landscape based on the water requirements of the plants. Many irrigation controllers have been developed for automatically controlling application of water to landscapes. Known irrigation controllers range from simple devices that control watering times based upon fixed schedules, to sophisticated devices that vary the watering schedules according to local geographic and climatic conditions.
With respect to the simpler types of irrigation controllers, a homeowner typically sets a watering schedule that involves specific run-times and days for each of a plurality of stations, and the controller executes the same schedule regardless of the season or weather conditions. From time to time the homeowner may manually adjust the watering schedule, but such adjustments are usually only made a few times during the year, and are based upon the homeowner's perceptions rather than actual watering needs. One change is often made in the late Spring when a portion of the yard becomes brown due to a lack of water. Another change is often made in the late Fall when the homeowner assumes that the vegetation does not require as much watering. These changes to the watering schedule are typically insufficient to achieve efficient watering.
More sophisticated irrigation controllers use evapotranspiration rates for determining the amount of water to be applied to a landscape. Evapotranspiration is the water lost by direct evaporation from the soil and plant and by transpiration from the plant surface. Potential evapotranspiration (ETo) can be calculated from meteorological data collected on-site, or from a similar site. One such system is discussed in U.S. Pat. No. 5,479,339 issued December, 1995, to Miller. Due to cost, most of the data for ETo calculations is gathered from off-site locations that are frequently operated by government agencies. Irrigation systems that use ETo data gathered from off-site locations are discussed in U.S. Pat. No. 5,023,787 issued June, 1991, and U.S. Pat. No. 5,229,937 issued July, 1993 both to Evelyn-Veere, U.S. Pat. No. 5,208,855, issued May, 1993, to Marian, U.S. Pat. No. 5,696,671, issued December, 1997, and U.S. Pat. No. 5,870,302, issued February, 1999, both to Oliver.
Due to cost and/or complicated operating requirements very few of these efficient irrigation controllers, discussed in the previous paragraph, are being installed on residential and small commercial landscape sites. Therefore, controllers that provide inadequate schedule modification primarily irrigate most residential and small commercial landscape sites. This results in either too much or too little water being applied to the landscape, which in turn results in both inefficient use of water and unnecessary stress on the plants. Therefore, a need existed for a cost-effective irrigation system for residential and small commercial landscape sites that is capable of frequently varying the irrigation schedule based upon estimates of actual water requirements. This need was met by U.S. Pat. No. 6,102,061, issued August, 2000 to Addink. However, there are thousands of manual irrigation controllers that have already been installed and are still being sold. Adjustments to these manual irrigation controllers are usually only made a few times during the year. The adjustments are based upon the homeowner's perceptions rather than actual watering needs of the landscape.
There are devices that can be connected to existing irrigation systems that will make automatic adjustments to the irrigation schedule, these interrupt or prevent one or more complete irrigation schedules from occurring. Examples of devices that interrupt or prevent the occurrence of planned irrigation schedules are rain sensors discussed in U.S. Pat. No. 4,613,764, issued September, 1986 to Lobato, U.S. Pat. No. 5,312,578, issued June, 1994 to Morrison et. al., U.S. Pat. No. 5,355,122 issued October, 1994 to Erickson, and U.S. Pat. No. 5,101,083, issued March, 1992 to Tyler, et al. There are other reasons for interrupting an irrigation schedule, such as; temperature extremes, high light intensity, high winds, and high humidity of which one or more of these are discussed in U.S. Pat. No. 5,839,660, issued November, 1998 to Morgenstern, et al., U.S. Pat. No. 5,853,122, issued December, 1998 to Caprio, U.S. Pat. No. 4,333,490 issued June, 1982 to Enter, S R., and U.S. Pat. No. 6,076,740, issued June, 2000 to Townsend. Additionally, there are patents that discuss the use of soil moisture sensors to control irrigation systems including U.S. Pat. No. 5,341,831, issued August, 1994 to Zur, U.S. Pat. No. 4,922,433, issued May, 1990 to Mark and U.S. Pat. No. 4,684,920 issued, August, 1987 to Reiter. However, as mentioned above, these devices, interrupt the operation of one or more full irrigation schedules or, as with the three above patents, rely on soil moisture sensors to control the irrigation applications. The disadvantage of soil moisture sensors is that the placement of the sensor(s) is critical to efficient irrigation.
What is needed is a cost effective device that will automatically modify the run-times of the irrigation schedules of installed irrigation controllers to affect irrigating of the landscape to meet the water requirements of the landscape plants based on some method or device other than a soil sensor.